Arc welding with controlled current pulses



1 1949. L. D. DRUGMAND 2,484,155

ARC WELDING WITH CONTROLLED CURRENT PULSES Filed March 2'7, 1948 rammed Oct. 11, 1949' :4- i a lzpgags-kii 14.4.

H. .i. 1-. ,izu'l'. Lester D. Drugmand, Greenfield, Wis, assignor to pofation of Deiavvare Cutler-Hammer, Inc., Milwaukee,;-Wis:',.acorlipplication March 27, 1948, Serial No. 17,455

The invention relates to electric welding systerns.

.The i ent n is spe iell suitable $9! re welding. In arc welding systerns proposed hereiefore xi r mean has? b R TP leQ t r ven diver ion i he ieeitip fr t th i nit n ireui thrash t rq e b th fins are eeerey a d a 'db'jefbmfi venee s F r fifs e without the e nployr'nent of"'sfich"ai'15iiliary fiiea'ns. Another object theinve'ntion is 'to' provide a welding systnfof' the -aforeicnenti'orled"t'yia' which i's'sirnple iii construction operation. Another 'otjet is"t5"p1ovide answer rnethod of 'c'ont'rolling'the initiation of Welding recur rent tp iid through v ncus'tyeeser electronic w. ',v l 4'1, "Le-i chili LxU-xl ,Ml L... i;

Ahother object is to provide a system which a oras' adjii'stn' e'nt' cf the Welding energy over u ,JI 3 1. J'.. H -15" Anothr'object is to provide a common means for -si'ir'iult'z ain'ofisly rendering eon-simme the welding" are gap and 'ele'ctron'tube which con trols' the welding "'er'gy supplied to said sweep. Another ob'ject istc pastime a ystem which afiords e'ach" dperation optionallfa singli'e' unia recuomrwemmgcurre t piilseqr a' pluraflityof i... L: 5, Ah! ,1 ,.".I- 1. n4 .1 2 .4;

' 'Otli'erobjects and advantages will appear from the"following ijescriptioni Ilie 'appe'r'icle trawl ng is illustrative of several ernloo'di'mentsdf the invention." In"thedr'eZwing, Figure 1 1s a 'si 'pnfie'd diagramilllistratingthe connections "of tHisystem when-using a -tube having a voltage' 'responsive -ignition"-electrode suchas disclosed in the Cox et alI'Patent'lWo. 2445,5 54; i'ss ued' July 2"0, 194$,"anli assigfied to the assigneof the"present?application?'- Fig. 2 is a modificatiori of the system illustrated in Fig. l, for use with a tube "'havinga responsive ignition'electrode such as usedin the ignition type tube. 'Fig. 3 illustrates an elaboration of the system illustrated in Fig. l'when supplied'withenergy from an alternating source,'while Fig. 4 is such an elaboration of the system illustrated in Fig. 2.

Referring to Fig. 1, one terminal of a source of welding'energy, which maybe a capacitor of a size suitable for the Work tobe performed,

is connected in series with'a welding electrode l I and a Welding arc gap ,I,2,;to a workpiece J3, the

latter constituting the second electrode ofthe'arc gap I2.' The circuit continues to the cathode electrode M ,The anode L4 isconnec tegl toth e second terminal of the capacitor ill: fllhe ignition electrode 1,4 7 is connected I through V afcont rol weasswitch {5, to one terminal of a source of ignition voltage 55, while the other terminal of said source is connected to the welding electrode i I.

' The-opereltion-of the-system illustrated in Fig. 1 is as follows: When-it is-desired to make a weldptheswitch leis-closed; thereby completing a circuit from the source-"i6, through the-switch l5; electrode I d y'cath'ode 14 workpiece l3; 1 are gap 'EZJele'ctrOde 'l lq'and' back to'the source it; If the polarity andpotential of the source it are"such as torender the electrode M sufficiently positive relative to the cathode M said potential ionizes the main" discharge path of tube and simultaneously the 'arc-"gap' is also.- Hence-a Weidin'g' current cause'd to flow from the capacifier Ni, through *tHetube'ME to workpiece t3, t6 the vvlding'electrodefl l5 and back to the cabacitor ll l'f The current will then continue' to flow a's long as the'iioltagehf the capacitor 19 is sufiici'na'y high to everceme the impedance of the'weldin 'eurre'n't circuit.- re" read- 0f capaitof m the source is an alternat nghurreh t soiirce, current will flow only cur iig t-Hos"altrrilite hs r "cycles'when the antes |4 p0siueeavah respet' t-e the -e'athoce id and the" igri'itioi'i' volta is positive with respect to the cathode during such l'ialf cyoles. ouwenew'iir flowduring-' sdch -altefiiate "lieu cycles as long aeswam &5 is 'close upply the f' i-l't L1} a rem micrieir ignition x/sledge.- J

' e f erri ri'lg nowto l ig". the system illustrated threbj aifr rsWr'orii the s 's'teih'--just de'scriloed that the'tube' 124 iso f"t he* aforementioned ignition typaaifd has at!" ign uc'iieleetrode fi l is current-responsive, e. requires Y that a four-rent rife." cifteiih ininin'lum magnitude be passed therethrou'ihfto Iitia'tfe" the" main di't'; charge of tlie tube. li clrcdit includin'g inseries with the souroe 'lii o fjigriitionpotentialthe prirn'ary Winding 'l 'i ofa'traii'sforrner is effective upon closure' or switcn fi afror supplying ignition current to the e ctrodejifi l flfheihfition current in] pulse nbvfmg in' wee -1mm weldin l a V ducesa iigfi voltage in these'condaiy'winding 5 1 which voltage is impressed upon the arc' "gap 12 toioni lie'the" samrw ereupon welding current 'fiows rrcmtheapacitm til, thro liglithetuhefi l and across the a'f gap 52 'back the capaCitOi, un til the voltageoffthe capacitor is'in'sufficieiit'to maintain n ercany ibng'er;*

"The arc'energv bfa single operation of the systends of t i i'gs; -'1 and '2 may-be'ee'ntroued by varyiiig'th energy storedin'tliecapacitorl0;" a'feffing to'rigif sja 'ternatin'g current supply insize z' l are 'cohnecteifto the primary winding zgbr'a tiansrorfiier 'gs; 'tv'hich ha's' else a "secondarv winding ZPYprOv'idedWvith -end termmai's gs 'a'ng "26, and witl'ifiri'terfnediate"terniinalsf ran former 3| has a secondary winding 3 l and another secondary winding 3 The secondary winding 33* of apeaking transformer 33 has one terminal connected to control electrode 32 of tube 32 in series with a current limiting resistor 40. A phase shifting network i comprising a capacitor 35 and in series therewith an adjustable resistor 36 is connected between the terminals 26 and 21 of transformer 23, while the primary winding 33 of the transformer 33 is connectedbetween the terminal 28 of transformer 23 and the common point of resistor 36 and capacitor 35. A Variable capacitor 3'! is connected in series with the rectifier 29 and switch 30, between the terminals 25 and 21, and a capacitor 38 has one of its terminals connected to the terminal 21 and its other terminal connected through the rectifier 34 to the terminal 28.

Connected in parallel with the capacitor 38 is a voltage divider 39, which has an adjustable tap connected to the second terminal of the winding 33*. The secondary winding 3| is connected across the arc gap 12 between the workpiece l3 and the welding electrode H. The workpiece is also connected to the line 20, while the electrode 3 i is also connected to the anode I l of a mercury tube I i of the type described in the aforementioned application. The tube M has a mercury pool cathode M and a voltage responsive ignition electrode 14 connected to one terminal of the winding 3I, while the other terminal of said winding 3 l is connected jointly with the cathode M and to the line 2|.

The operation of the system illustrated in Fig. 3 is as follows: Let the half cycle of the alternating line voltage during which the line 2| is positive with respect to line and the terminal of the winding 24 is positive with respect to the terminal 23, be called the positive half cycle of the alternating voltage. With the lines 20 and 2| energized, the capacitor 38 is charged during the positive half cycle so that its voltage renders the control electrode 32 negative with respect to the cathode 32 The charge of the capacitor 38, which leaks off through the potentiometer resistor 39 during the intermediate negative half cycles is insignificant, so that it may be assumed that the potential of the capacitor is substantially constant. At the same time a current derived from the phase shift network 35-36 passes through the primary winding 33 of the peaking transformer 33. The phase displacement of said current relative to the aforementioned positive half cycle is determined by the adjustment of the resistor 36 of the phase shift network 3536. The current in winding 33 induces a peaked alternating voltage in the winding 33, the polarity being such that the positive peak occurs during the negative half cycle of the line voltage. This peak voltage is superposed upon the aforementioned unidirectional voltage of the capacitor 38 so that the peak of the sum of the two voltages is sufficient to afford ignition of the tube 32 when the anode 32 is positive with respect to the cathode 32. If now the switch is closed, the capacitor 3'! is substantially instantaneously charged during the positive half cycle of the alternating voltage, so

. 32 is connected to the terminal 21. The transthat the capacitor plate which is connected to the anode 32 is positive. This charge takes place substantially at the beginning of each positive half cycle. The charged condenser 3? thus renders the anode 32 positive with respect to the cathode 32 and at the moment of the succeeding negative half cycle determined by the setting of the phase shifting network -46, the tube 32 is rendered conducting to discharge the capacitor 31. The discharge current passes through the winding i of transformer 3i and induces voltages in the secondary windings 3i and 31. The former causes an ignition discharge to pass between the workpiece i3 and the electrode I i, while the latter impresses simultaneously an ignition potential between the cathode M and the ignition electrode is, thus initiating currentfiow from the line 29, through the arc gap l2, and the tube It, back to line 2 I. This current will cease to how at the end of the negative half cycle. If at or before the beginning of the next succeeding positive half cycle the switch 5c has been opened, the capacitor 3f will not be charged again, it being so proportioned with respect to tne impedance of the discharge circuit that it will be substantially discharged by a single pulse of current through the tube 32. If during such next succeeding positive half cycle the switch is stiii'neld closed, conduction of the tube it and of the arc gap l2 will again be initiated in the manner aforedescribed so as to supply additional welding impulses to the arc gap l2.

It will be apparent that the moment of initiation of flow of welding energy and its effective value during a given half cycle may be determined by tne adjustment of the phase shifting network, while the total number of such current pulses is regulated by the time of closure of switch 38.

The system illustrated in Fig. 4 is similar to that aforedescribed in connection with Fig. 3, except as will be .pointed out hereinafter. The tube M of Fig. 3 is replaced by an ignitron tube 24, which has a cathode fil an anode 24 and a current responsive ignition electrode 24. The transformer 's'i of Fig. 3 is replaced by a transformer ll which has a primary winding ll connected between the positive terminal of capacitor 31 and the ignition electrode 24. A secondary winding 11 of transformer ll replaces the winding 31 of Fig. 3. The secondary winding 36 of Fig. 3 is omitted.

The system of Fig. 4 operates similarly to the aforedescribed system shown in Fig. 3, except as follows: The discharge current of capacitor 31 passes through the primary winding it over the current responsive ignition electrode 2%, cathode 24 thence through tube 32, back to capacitor 31. This induces a voltage in the winding l'l which produces an ignition discharge across arc gap I2. Hence the arc gap between the electrode H and the workpiece i3, and the tube 2 3 are simultaneously ionized and the Welding current flows during predetermined periods through the welding arc gap, as has been explained heretofore.

The moment of starting of welding current flow during the negative half cycle of the line voltage and hence the total weldingenergy may be adjusted by adjusting the phase shift network 35-3B as aforedescribed in connection with Fig. 3.

As will be apparent in the systems of Figs. 3 and 4, welding current supplied by the lines 202I flows during a succession of negative half cycles while the switch 30 is closed.

What I claim as new and desire to secure by Letters Patent is f Y 1. In a welding system, the combination wit a work-piece, a cooperating welding electrode, an arc gap intervening between the latter and the former, a source of welding energy and an electron tube having a main discharge path and a control electrode, of connections to provide a first circuit including in series with each other said source, said main discharge path of said tube and said arc gap, and a second circuit for said control electrode, the cathode of said tube and said are gap providin for ionization of said arc gap as a function of current flow between said ontrol electrode and said cathode, and means to impress a pulse of ignition energy upon said last named circuit for initiating the flow of welding current through said first named circuit.

2. In a welding system, the combination with a Work-piece, a cooperating welding electrode, an arc ap intervening between the latter and the former, a source of welding energy and an electron tube having a main discharge path and a control electrode, of a switch, a source of ignition voltage, and connections to provide a first circuit includin in series with each other said source, said main discharge path of said tube and said are gap, and a second circuit including in a functionally series relation with each other said switch, said source of ignition voltage, said ignition electrode, the cathode of said tube and said are gap to afford simultaneous initiation of current flow through said are gap and said tube.

3. In a welding system, the combination with a work-piece, a, cooperating welding electrode, an arc gap intervening between the latter and the former, a source of welding energy and an electron tube having a main discharge path and a control electrode, of connections to provide a first circuit including in series with each other said source, said main discharge path or said tube and said are gap, and a second circuit including in series with each other said ignition electrode, the cathode of said tube, said are gap, a source of control voltage and a switch operable to close said second circuit for ionizing said tube and said are gap to initiate flow of welding current through said first named circuit.

4. In a welding system, the combination with a work-piece, a cooperating welding electrode, an

arc gap intervening between the latter and the former, a source of welding energy and a gaseous electron tube having a main discharge path and an ignition electrode efiective to ionize said main discharge path in response to a given current supplied to said electrode, of connections to provide a first circuit including in series with each other said source, said main discharge path of said tube and said are gap, a transformer having a primary and a secondary winding, a second circuit including in series with each other said ignition electrode, the cathode of said tube and said primary winding, and means to impress a pulse of ignition energy upon said second circuit, and a third circuit including said secondary winding and said arc gap.

5. In a welding system, the combination with a workpiece, a cooperating welding electrode, an arc gap intervening between the latter and the former, a source of welding energy and a gaseous electron tube having a main discharge path and an ignition electrode effective to ionize said main discharge path in response to a given current supplied to said electrode, of connections to provide a first circuit including in series with each other said source, said main discharge path of said tubeand said are gap, a transformer having a primary and a secondary winding, a second circuit including in series with each other said ignition electrode, the cathode of said tube, said primary winding, a source of ignition current and a switch operable to close said second circuit, and a third circuit including said secondary winding andsaid arc gap.

6. In a welding system, the combination with a workpiece, a cooperating welding lectrode, an arc gap intervening between the latter and the former a source of welding energy and a gaseous electron tube having a main discharge path and an ignition electrode, of circuit connections including in series with each other said source, said main discharge path of said tube and said are gap, a capacitor, means to charge said capacitor to a given potential, means to discharge said capacitor at will, and means to impress at least a part of the discharge energy of said capacitor simultaneously upon said are gap and said ignition electrode.

7. In a welding system, the combination with a workpiece, a cooperating welding electrode, an arc gap intervening between the latter and the former, an alternating current source, a gaseous electron tube having a main discharge path and an ignition electrode, of circuit connections including in series with each other said source, said main discharge path of said tube and said are gap, a capacitor, means including rectifying means to charge said capacitor substantially in stantaneously from said source while said source has a given polarity, means operative to discharge said capacitor while said source has the opposite polarity, including means to time initiation of discharge with respect to the phase angle of the alternating current from said source, and means to impress at least a part of the discharge energy of said capacitor simultaneously upon said are gap and said ignition electrode.

8. In a welding system, the combination with a workpiece, a cooperating welding electrode, an arc gap intervening between the latter and the former, an alternating current source, a gaseous electron tube having a main discharge path and an ignition electrode, of circuit connections to provide a first circuit including in series with each other said source, said main discharge path of said tube and said are gap, a capacitor, means including rectifying means to charge said capacitor substantially instantaneously from said source while said source has a given polarity, a second gaseous electron tube having a control electrode and having its main discharge path connected in shunt across said capacitor, a phase shifting network connected to said source and arranged to normally impress a potential upon the control electrode of said second tube to render said tube non-conducting during half periods of one polarity of said source, means operative to vary said last named potential for rendering the tube conducting to discharge said condenser during half periods of the opposite polarity of said source and means to impress at least part of the energy of discharge of said capacitor simultaneously upon said are gap and said ignition electrode.

9. In a welding system, the combination with a workpiece, a cooperating welding electrode, an arc gap intervening between the latter and the former, an alternating current source, a gaseous electron tube having a main discharge path and an ignition electrode, of connections to provide a first circuit including in series with each other said source, said main discharge path of said tube 7 and said are gap, a capacitor, means including a half wave rectifier adapted to charge said capacitor to a given potential with rectified energy from said source, a second gaseous electron tube having a control electrode and having its main discharge path connected in shunt across said capacitor, a phase shifting network connected to said source and arranged to normally impress a potential upon the control electrode of said second tube to render said tube non-conducting, means to vary No references cited.

Certificate of Correction Patent No. 2,484,155 October 11, 1949 LESTER D. DRUGMAN D It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 42, and column 2, line 34, for the word ignition read igm'iron; column 6, line 12, after former insert a comma;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 31st day of January, A. D. 1950.

THOMAS F. MURPHY,

Aan'atant Oommiaaioner of Patenta. 

